The field of the present invention is manufacturing methods for heat-resistant, high-strength structural members made of sintered aluminum alloy.
Lightweight alloys such as aluminum alloys are highly suitable for the moving parts of an internal combustion engine since they have low inertia and lighten the weight of the entire engine. In particular, parts made of sintered aluminum alloys by powder metallurgy methods greatly contribute to improved engine performance due to their increased heat resistant, strength, and Young[s modulus obtained by the addition of various kinds of alloying elements.
Conventionally, heat-resistant, high-strength parts made of a sintered aluminum alloy and containing a large amount of iron and silicon are formed by compressing metal powder into a billet which is then extruded to form a rod. The rod is then hot forged to form the desired part. However, if a preheated material for the hot forging is put into a forging metal mold, the material is cooled by the metal mold, resulting in degradation of the ductility of the material and the formation of cracks during the hot forging. To prevent these problems, it is effective to employ a constant temperature forging method in which forging is performed using a heated metal mold. However, complicated and large-sized equipment is required to maintain the metal mold and the material at a predetermined temperature. These requirements increase the cost of the resulting products.